[mitchtr25068@aol.com]

On my 2014 328d, I’ve had check engine light on for weeks, and code reader says

P20BD
Reductant heater b
Control circuit/open
Permanent

Any thoughts on why/where/how and what to fix? I’ve never heard of a reductant heater and haven’t located it yet in my Bentley book. Thanks!

[Enabled]

See if you can get a code read with a tool that reads BMW manufacturer codes. P codes can be vague and sometimes misleading. Sometimes there are 2-3 detailed manufacturer codes to a single P code.

[montr]

I do not have a 328d but I have a 335d. For the 335d it is either the AdBlue heater or the temperature sensor in the SCR tank (AdBlue)

[mitchtr25068@aol.com]

I did more research on the code and found a company called xemodex in Canada that makes a urea heater and sensor repair kit, with the option to have them rebuild the system or do it yourself with a very detailed 30-plus page guide. I’ve got it in order and will report back

https://xemodex.com/us/product/def-s...-bmw-3-series/

[Enabled]

Did you check with them if it applies to the F30 chassis?
All those pics look like it's for the E90 335d.

[JohnZJr]

We have a 2015 X3d with the same issue. Lots of information on this code for other than BMWs. One common item we found was that this code should not exist unless it is cold out and DEF heater is attempting to turn on. This is happening at 80-90F. No symptoms other than check engine light is on. Got the permanent code to reset and check engine light turn off for a short period (50 miles). Threads for other vehicles indicate this is a programming issue, not a heater failure. Tried filling the DEF tank to overflow. Another suggestion was to drain the tank, refill with warm water to dissolve salts that can form. Any additional thoughts?

[Enabled]

A circuit error is most definitely a broken connection or a fault with the component described.

Do you have any additional codes?

[JohnZJr]

80518A and 244800 show up sometimes. Not permanent codes.

[andreigbs]

Bump up for the same/similar issue here: SCR dosing heater open to short causing CEL. I can reset the error and it even regens just fine. I'm thinking either the SCR module is faulty or the wiring to/from it somewhere is damaged.

Going to inspect the wiring first, then look at metering valve itself. If it's the valve itself, a new one costs about $270 (part #18-30-8-514-448).

[Enabled]

You can put a used one in just fine, if you find one for cheap.

FWIW, the regens have nothing to do with the SCR/DEF system.

[andreigbs]

My understanding is that the SCR system is part of the regen process, insofar as the DPF needs to be scrubbed from time to time of accumulated ash solids. I welcome additional insight.

I'm hoping that it's just something with the wiring but I'm prepared to remove the metering valve, clean up any crystal solids that may be built up and even replace the module itself. What I hate is having to reset the CEL every other start-up...

[Enabled]

The DEF is sprayed onto the hot SCR brick, which is well downstream of the particulate filter, somewhere about mid car. The heat evaporates the water content, leaving urea, which then generates the active components, ammonia and isocyanic acid.

It's designed to convert the NOx gases into nitrogen gas, water vapor, and carbon dioxide gas. It isn't related to particulates, and the SCR system operates completely separate of DPF and other regen catalysts.


The dpf processes the particulates and ash. DPF is a fairly large honeycomb structure that catches the bigger particles, and stores them until they are burned off at high temperatures, either actively or passively. Contrary to internet myth, it isn't very restrictive at all.

Depending on different emissions setups across manufacturers, there are a few other catalyst functions to catch NOx, sulfur, and oxides, each with very specific regen routines.

[andreigbs]

That's helpful, thanks for explaining it. Agreed, I don't think the DPF is a big restriction. Unless one is using a full SAPS oil, burning some, not having the DPF regen properly.

I will have to carefully inspect the SCR module wiring, I'm hoping it's something as simple as a tear/break in the circuit and not the actual module itself, since just a few weeks ago the SCR system was working fine at -19*C cold snap we had a couple of days.

[Enabled]

Just for clarification, it's not the SCR control module itself that you'd be looking at. Are you using ISTA to read the codes? What exact codes?
What does the test plan say?
I'm looking to see where the heater would be located. It may or may not be part of the sprayer (aka 'metering unit').

[andreigbs]

You are correct, I should have said the sprayer which has the integrated heating element attached.

The SCR sprayer unit is part# 18-30-8-514-448, part #14:
https://www.bmwpartswholesale.com/oe...it-18308514448

I don't have ISTA, I'm using BimmerLink. The expanded info from the error reads:

"Code 8051C5 - Doing line heating, control: Short circuit to ground (DFC_UHtrPLSCG, Pin6)"

What I can't seem to find is the wiring harness that connects the sprayer/heater unit to the DEF tank in the back. It's probably a pain to replace at the tank connection, compared to replacing the unit from where it plugs into the exhaust stream. Here's a PDF of the SCR system showing where the spray module plugs in (Page 68): https://documentcloud.adobe.com/link...7-aab2d33ac550

[andreigbs]

Update: local Milwaukee BMW dealer diagnosed it as a failed DEF metering line. Gave me an estimate of $1200 to replace the 2 parts involved. The line itself is $250ish (part # 16-19-7-286-301) and the required bracket is $15ish (part # 16-19-7-286-305).

They charge double that for parts and 5 hours of labor

This may be the impetus I need to finally get it tuned and turn off the DEF system. Unless there's a how-to document or post to guide me into changing it out myself, for which I'd be grateful.

[Enabled]

Originally Posted by andreigbs

Update: local Milwaukee BMW dealer diagnosed it as a failed DEF metering line. Gave me an estimate of $1200 to replace the 2 parts involved. The line itself is $250ish (part # 16-19-7-286-301) and the required bracket is $15ish (part # 16-19-7-286-305).

They charge double that for parts and 5 hours of labor

This may be the impetus I need to finally get it tuned and turn off the DEF system. Unless there's a how-to document or post to guide me into changing it out myself, for which I'd be grateful.

https://www.newtis.info/tisv2/a/en/f...ogy/1VnciQMP5y


And more here:

https://www.newtis.info/tisv2/a/en/f...on-technology/

[andreigbs]

Thanks @Enabled, that looks doable. Then I looked at lowering the real axle support which is probably where I'd run into trouble, to be honest.

I wonder how critical those special tools are, and if anyone has found workarounds when you don't have them?

[Enabled]

Most of the special tools can be replaced with something else or a different procedure.

I'd be curious first as to what is defective, instead of just swapping parts thought.

You might be able to skip the big suspension drop, but with some investigating first.

[andreigbs]

I believe there's a break in the circuit, but I couldn't see any obvious breakage of wires, plugs, or harness. It was quite cold this past winter, getting down to -20*F on my drive to work, it's possible the heating element burnt itself out or burnt wire(s) along the DEF heater line. But again, I don't see anything obvious on the outside looking up and down the line itself.

[S4NoMore]

Originally Posted by andreigbs

I believe there's a break in the circuit, but I couldn't see any obvious breakage of wires, plugs, or harness. It was quite cold this past winter, getting down to -20*F on my drive to work, it's possible the heating element burnt itself out or burnt wire(s) along the DEF heater line. But again, I don't see anything obvious on the outside looking up and down the line itself.

Did you ever sort this out? I'm at the same point, I have a CEL for this code as well on my 2015 X3d. Unsure about whether the issue is the metering unit, which seems doable, or the line, which is daunting with a subframe drop.

[andreigbs]

Originally Posted by S4NoMore

Did you ever sort this out? I'm at the same point, I have a CEL for this code as well on my 2015 X3d. Unsure about whether the issue is the metering unit, which seems doable, or the line, which is daunting with a subframe drop.

I had my local dealer look at it, they quoted me close to $1400 to replace the line. I opted to delete the code and see if it comes back. Fortunately I haven't had to drive a lot the past year and I've put off doing the repair.